Genetic diversity and natural selection Flashcards
define genetic diversity
differences in DNA/base sequence/ alleles
in a gene pool
define natural selection
individuals with particular characteristic have greater chance of survival than without
so more likely to breed + pass on these characteristics
these characteristics increase in frequency over generations
define population
group of interbreeding individuals of the same species
define gene pool
collection of different genes within interbreeding populations
define alleles
different versions of the same genes
define allele frequency
how often a particular allele occurs within a population
what’s the link between natural selection and evolution
natural selection = -central mechanisms of evolutionary change
- process responsible for evolution of adaptive features
what is natural selection
a process
which leads to evolution
what is evolution
change in allele frequency
over many generations in a population
what types of adaptations are there
anatomical
physiological
behavioural
what is the process of natural selection
new alleles by random mutations
if new allele increase chance of survival in environment = more likely to survive + reproduce
reproduction= passes on advantageous allele to next generation
define selective pressure
causes natural selection e.g antibiotic resistance
what are the two types of natural selection
selective
directional
what is directional selection
one of the extremes has selective advantage
occurs when change in environment
modal trait changes
what is stabilising selection
modal trait has advantage
occurs when no change in environment
modal trait remains the same
standard deviation decreases as individuals with extreme trait decreases
how does genetic diversity occur
mutation: deletion, addition, substitution, nucleotide
deletion/ translocation of chromosomes
aneuploidy, polyploidy
meiosis: independent segregation
random fertilisation
crossing over
how can genetic diversity be increased
crossing over independent segregation genetic mutations outbreeding immigration
what is the importance of genetic diversity
greater genetic diversity = species more likely to adapt to changes in environment
because wider range of alleles so wider range of characteristics
anatomical adaptations are
structural features e.g bright coloured feather
physiological adaptations are
processes inside the body /e.g hibernation
behavioural adaptations are
the way an organism acts e.g birds with elaborate mating rituals
what is the process of natural selection for evolution of populations
- variations of alleles in population, due to random DNA mutations
- selection pressure/change in environment
- advantageous allele = increased chance of survival + reproduction = reproductive success
- advantageous allele passed onto offspring
- frequency of advantageous allele + characteristic increases in population
- over many generations
what is artificial selection
when humans decide what members to breed
what does artificial selection do
allows desirable alleles to be maintained
